In Mac OS X, applications usually come in a package that contains resources for several different display languages. By default, an application is launched in the language the system is set to. So if you, say, wanted to launch a specific application in German, but your default system language is English, you couldn’t achieve this easily.
Add contextual menu in Finder
But there’s a handy plugin named LaunchAppPlugin that installs into the Finder’s contextual menu. When installed, you simply right-click an application icon, select Launch [App name] in (where [App name] is the name of the selected app) and select the language to launch the application in. The plugin shows all the languages available in the application’s package and the selection is only temporary. The next time the app is launched, it will use the system default language again.
LaunchAppPlugin is freeware and available from Arizona Software. It runs on Mac OS X 10.3.9 and newer.